#include "stdafx.h"
#include "stream_reader.h"

void CStreamReader::construct				(
		const HANDLE &file_mapping_handle,
		const u32 &start_offset,
		const u32 &file_size,
		const u32 &archive_size,
		const u32 &window_size
	)
{
	m_file_mapping_handle		= file_mapping_handle;
	m_start_offset				= start_offset;
	m_file_size					= file_size;
	m_archive_size				= archive_size;
	m_window_size				= _max(window_size,FS.dwAllocGranularity);

	map							(0);
}

void CStreamReader::destroy					()
{
	unmap						();
}

void CStreamReader::map						(const u32 &new_offset)
{
	VERIFY						(new_offset <= m_file_size);
	m_current_offset_from_start	= new_offset;

	u32							granularity = FS.dwAllocGranularity;
	u32							start_offset = m_start_offset + new_offset;
	u32							pure_start_offset = start_offset;
	start_offset				= (start_offset/granularity)*granularity;

	VERIFY						(pure_start_offset >= start_offset);
	u32							pure_end_offset = m_window_size + pure_start_offset;
	u32							end_offset = pure_end_offset/granularity;
	if (pure_end_offset%granularity)
		++end_offset;

	end_offset					*= granularity;
	if (end_offset > m_archive_size)
		end_offset				= m_archive_size;
	
	m_current_window_size		= end_offset - start_offset;
	m_current_map_view_of_file	= (u8*)
		MapViewOfFile(
			m_file_mapping_handle,
			FILE_MAP_READ,
			0,
			start_offset,
			m_current_window_size
		);
	m_current_pointer			= m_current_map_view_of_file;

	u32							difference = pure_start_offset - start_offset;
	m_current_window_size		-= difference;
	m_current_pointer			+= difference;
	m_start_pointer				= m_current_pointer;
}

void CStreamReader::advance					(const int &offset)
{
	VERIFY						(m_current_pointer >= m_start_pointer);
	VERIFY						(u32(m_current_pointer - m_start_pointer) <= m_current_window_size);
	int							offset_inside_window = int(m_current_pointer - m_start_pointer);
	if (offset_inside_window + offset >= (int)m_current_window_size) {
		remap					(m_current_offset_from_start + offset_inside_window + offset);
		return;
	}

	if (offset_inside_window + offset < 0) {
		remap					(m_current_offset_from_start + offset_inside_window + offset);
		return;
	}

	m_current_pointer			+= offset;
}

void CStreamReader::r						(void *_buffer, u32 buffer_size)
{
	VERIFY						(m_current_pointer >= m_start_pointer);
	VERIFY						(u32(m_current_pointer - m_start_pointer) <= m_current_window_size);

	int							offset_inside_window = int(m_current_pointer - m_start_pointer);
	if (offset_inside_window + buffer_size < m_current_window_size) {
		Memory.mem_copy			(_buffer,m_current_pointer,buffer_size);
		m_current_pointer		+= buffer_size;
		return;
	}

	u8							*buffer = (u8*)_buffer;
	u32							elapsed_in_window = m_current_window_size - (m_current_pointer - m_start_pointer);

	do {
		Memory.mem_copy			(buffer,m_current_pointer,elapsed_in_window);
		buffer					+= elapsed_in_window;
		buffer_size				-= elapsed_in_window;
		advance					(elapsed_in_window);

		elapsed_in_window		= m_current_window_size;
	}
	while (m_current_window_size < buffer_size);

	Memory.mem_copy				(buffer,m_current_pointer,buffer_size);
	advance						(buffer_size);
}

CStreamReader *CStreamReader::open_chunk	(const u32 &chunk_id)
{
	BOOL						compressed;
	u32							size = find_chunk(chunk_id,&compressed);
	if (!size)
		return					(0);

	R_ASSERT2					(!compressed,"cannot use CStreamReader on compressed chunks");
	CStreamReader				*result = new CStreamReader();
	result->construct			(file_mapping_handle(),m_start_offset + tell(),size,m_archive_size,m_window_size);
	return						(result);
}

#include "FS_impl.h"
u32 CStreamReader::find_chunk				(u32 ID, BOOL* bCompressed)
{
	return inherited::find_chunk(ID, bCompressed);
}